First-principles self-consistent total-energy calculations within the local-density approximation show, in agreement with experiments, that CsI undergoes a transition from the cubic (CsCl) structure to a tetragonal structure at a pressure $P_t\simeq 40$ GPa. The calculated volume at the transition is ∼ 53% of the zero-pressure volume. We find that the phase transition is driven by an "intercellular" electrostatic interaction. A structural bistability is found around the transition.

• Received 6 May 1985

DOI:https://doi.org/10.1103/PhysRevLett.55.600